1. Field of the Invention
The present invention is a fire detection system that distinguishes a false alarm from a real alarm by requiring a predetermined number of alarm signals from the fire sensor during an observation period.
2. Prior Art
A fire warning system is disclosed in U.S. Pat. No. 3,842,409, in which the output of a fire sensor is converted into successive pulses activating a shift register to supply an output. It uses a capacitor independently repeating its charging and discharging cycle to supply the input to the data terminal of the shift register. After the output of the fire sensor blocks the line for discharging the capacitor, the voltage across the capacitor continues unchanged at the data terminal. The shift register shifts this signal supply to supply its output by receiving clock pulses. However, it does not distinguish the start of a fire from causes other than a fire, even if the fire sensor sends a continuous output signal.